Information recording apparatus

ABSTRACT

An information recording apparatus for recording data by applying energy to a recording medium to form thereon local physical changes of the medium includes a space length discriminating unit for discriminating a space length of a space in a channel data sequence when data is recorded, and a recording energy irradiating unit for generating at least two recording waveforms when successive spaces having a same length in the channel data sequence are recorded, in accordance with results discriminated by the space length discriminating unit. The at least two recording waveforms may be at least two mutually different recording waveforms.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an information recordingapparatus, particularly an optical disk drive, which records data byapplying energy to a recording medium to form thereon local physicalchanges of the medium.

[0003] 2. Description of the Related Art

[0004] Optical disks currently prevailed are roughly divided intomagneto-optical disks and phase change disks. In the case ofmagneto-optical disks, a mark of an inverted magnetic domain is formedon a recording film by heating the film, and in the case of phase changedisks, a mark of an amorphous region is formed on a recording film bychanging a cooling speed of the film under the control of an energyamount when it is heated. In order to increase a recording density ofsuch optical disks, the size of a data carrying mark is reduced, or eachchange unit of the mark length and space length is made short to narrowa time interval between mark edge detections. In each of these methods,it is essential to form a mark at a high precision. It is verydifficult, however, to stably and highly precisely form a fine markabout a half of a light spot diameter. This is because a fine mark isrequired to be formed on a recording film at an area having a gentlespatial temperature gradient of the film whose temperature is raised bya light spot, particularly at an area having the gentle spatial peaktemperature gradient. If an effective recording sensitivity of arecording film varies, because of a change in the peak temperature ateach mark caused by a change in a recording film temperature beforeapplication of recording energy or by a change in the recording energyintensity, the mark shape is deformed greatly. In the case of an opticaldisk of the type that the mark shape is controlled by a recordingwaveform, a peak temperature of a recording film is likely to fluctuatedepending upon a recording pattern. A shortest approach to solving thisproblem is to use a light source of short wavelength laser to reduce thelight spot diameter. However, wavelengths of current semiconductor laserdiodes as typical laser light sources are still unsatisfactory in orderto meet the requirements of increasing a recording density.

[0005] It is therefore necessary to select a recording waveform hard topose such problems, in order to reliably form a fine mark and performhighly reliable recording/reproducing. The problems associated with arecording waveform to be solved are the following two problems. Thefirst problem is related to suppression of thermal crosstalk touniformly form nearby marks independently from the intervaltherebetween. The second problem is related to a constant heataccumulation to uniformly form consecutive marks independently fromtheir lengths. If the thermal crosstalk suppression and constant heataccumulation can be realized, edge shifts of a reproduction signal canbe suppressed so that a mark edge recording method suitable for highlinear recording density can be adopted. If constant heat accumulationcan be realized, reproduced crosstalk can be made constant so that thetrack interval can be shortened and the recording area density can beimproved.

[0006] In a first conventional technique of solving the above problemsdisclosed in JP-A-5-298737, the recording waveform corresponding to amark forming period is constituted of a series of pulse trainscorresponding to the lengths of marks in a channel data sequence. Thenumber of pulses and the width of pulses are controlled in accordancewith the lengths of marks in the channel data sequence. The recordingwaveform corresponding to the mark forming period is divided into twoportions, a front portion and a succeeding portion, and generally theheight of each pulse is different. In a mark non-forming period of therecording waveform, a space portion is provided before an auxiliaryrecording pulse which is generated during this period. The mark formingperiod reflects the length of a mark in the channel data sequence, andis defined as shown in FIG. 4 at (c) as a period from the first pulseleading edge to the last pulse trailing edge, the pulse having an energylevel sufficient for supplying energy of recording a mark, i.e., thepulse having such an energy level as a mark cannot be formed withoutthis level. The mark non-forming period reflects the length of a spacein the channel data sequence, and is defined as a period other than themark forming period. The above definitions are applied also to thefollowing description of this specification. The first conventionaltechnique with the above-described structure holds the position thatthermal diffusion directly from the preceding mark formed portion to theimmediately succeeding mark leading edge can be compensatedindependently from the space length, and that the mark width and markedge position can be controlled at high precision.

[0007] In a second conventional technique of solving the above problemsdisclosed in JP-A-1-078437, with reference to the length of a precedingmark non-forming period, a portion of the recording waveformcorresponding to the immediately succeeding mark forming period is madevariable. Specifically, as illustrated in FIG. 4 at (a), a recordingenergy irradiating means is provided which with reference to the lengthsof preceding spaces 401 and 403, the recording waveforms correspondingto marks 402 and 404 are controlled, or more precisely, the leading edgeforming positions of the marks 402 and 404 are controlled. This secondconventional technique holds the position that thermal diffusiondirectly from the preceding mark formed portion to the immediatelysucceeding mark leading edge can be compensated independently from thespace length, and that the mark width and mark edge position can becontrolled at high precision.

[0008] Another conventional technique disclosed in JPA-5-143993describes that if the blanking period between an immediately precedinglight pulse and a current light pulse is short, heat generated by theimmediately preceding light pulse influences the current light pulse andtherefore this preheat effects are made to have the same effects as thelong blanking period, and that the energy level and width of a lightpulse supplied from a bias light irradiating unit provided immediatelybefore the current light pulse are determined in accordance with themeasured pulse width of the preceding light pulse and the measuredblanking period.

[0009] Regarding the first problem, although each of the conventionaltechniques changes the conditions of forming a leading edge of asucceeding mark, this condition change is not satisfactory. Furthermore,each of the conventional techniques does not take into consideration thecompensation for the thermal diffusion near to the leading edge formingposition of an immediately succeeding mark in accordance with the levelof the energy amount used for the formation of the preceding mark.Therefore, only if the preceding mark forming periods are constant, thesucceeding mark can be reliably formed irrespective of the length of themark non-forming period between two marks. However, if the immediatelypreceding mark forming period changes, it is difficult to form theleading edge of a succeeding mark at a target position even if the marknon-forming period between two marks is constant. Namely, the longer thepreceding mark forming period, the more the heat energy used for theformation of the preceding mark diffuses near to the leading edgeforming position of the immediately succeeding mark, and the nearer theleading edge comes to the trailing edge of the immediately precedingmark. The above phenomena become more conspicuous as the linearrecording density is raised or the mark non-forming period between twomarks becomes short.

[0010] Regarding the second problem, each of the conventional techniquesis unsatisfactory with respect to the constant heat accumulation, andcannot suppress sufficiently a shift of the trailing edge from a targetposition depending upon the mark width, if the mark width is shortenedand the linear recording density is raised. Namely, the trailing edgeposition and mark width fluctuate depending upon the distance from themark leading edge. The above phenomena become conspicuous as the linearrecording density is raised.

[0011] From the above reasons, therefore, each of the above conventionaltechniques cannot form a fine mark at a sufficiently high precision andtherefore cannot realize a sufficient recording area density.

SUMMARY OF THE INVENTION

[0012] In order to solve the first problem, the invention provides aninformation recording apparatus for recording data by applying energy toa recording medium to form thereon local physical changes of the medium,the information recording apparatus comprising: recording energyirradiating means for generating at least two recording waveforms whenmarks or spaces of the same length in a channel data sequence arerecorded.

[0013] In order to solve the first problem, the invention furtherprovides an information recording apparatus for recording data byapplying energy to a recording medium to form thereon local physicalchanges of the medium, the information recording apparatus comprising:recording pattern analyzing means for analyzing a recording pattern in achannel data sequence when data is recorded; and recording energyirradiating means for generating at least two recording waveforms whenmarks or spaces of the same length in the channel data sequence arerecorded, in accordance with the analyzed results by said recordingpattern analyzing means.

[0014] The recording pattern includes information on the lengths ofmarks and spaces, the sequential orders of marks and patterns and otherinformation. The recording waveform indicates how a recording energy isapplied to a recording medium, i.e., a time sequential change in arecording energy level.

[0015] As described above, the conditions of forming the leading edge ofa succeeding mark are precisely compensated with respect to the spacelength immediately after the preceding mark. Furthermore, thermaldiffusion near to the leading edge forming position of an immediatelysucceeding mark is compensated depending upon the energy amount used forforming the immediately preceding mark. In the above manner, a mark canbe formed reliably independently from the length of the immediatelypreceding mark and the length of a space between two marks.

[0016] In order to solve the second problem, the invention provides aninformation recording apparatus for recording data by applying energy toa recording medium to form thereon local physical changes of the medium,the information recording apparatus comprising: recording energyirradiating means for generating a recording waveform during a markforming period, the upper and lower envelopes of the recording waveformlowering as a time lapses from the start of the mark forming period.

[0017] As above, heat accumulation when a long mark is formed can becompensated precisely, and the trailing edge of a long mark can beformed precisely at a target position independently from the marklength.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a diagram illustrating the structure of a disk drive ofthis invention.

[0019]FIG. 2 is a diagram illustrating recording waveforms of theinvention.

[0020]FIG. 3 is a diagram showing the structure of a recording block ofthe disk drive of the invention.

[0021]FIG. 4 is a diagram illustrating the operation of a recordingpattern analyzer of the invention.

[0022]FIG. 5 is a diagram illustrating the operation of the recordingpattern analyzer of the invention.

[0023]FIG. 6 is a diagram illustrating the operation of the recordingpattern analyzer of the invention.

[0024]FIG. 7 is a diagram illustrating the effects of high precisionmark formation of the invention.

[0025]FIG. 8 is a diagram illustrating different configurations ofrecording waveforms.

[0026]FIG. 9 is a diagram showing the structure of a recording patternanalyzer of an information recording apparatus of this invention.

[0027]FIG. 10 is a diagram illustrating the operation principle andeffects of the information recording apparatus of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Embodiments of the invention will be described. In theembodiments, a magneto-optical recording medium will be described as anexample of a recording medium. The recording medium is not limited onlythereto, but the techniques disclosed in the embodiments are shared byother recording media so long as they are of the type that data isrecorded by applying energy to the recording medium to form localphysical changes thereon. Also in the embodiments, although a recordingwaveform which changes only a single parameter will be described, theconfiguration of a recording waveform of this invention is not limitedthereto. For example, although a recording waveform shown in FIG. 8 at(a) can be definitely identified by designating parameters Pa, Pb, Pw1,Pw2, Tb, Tw1, Tw2 and Tbw, a different configuration of a recordingwaveform with its parameters being all different may also be used. Achanging portion of a recording waveform may be a mark forming area, amark non-forming area, or both areas. Parameters identifying a recordingwaveform are illustrative and are not limited thereto, but otherconfigurations of a recording waveform identified with parametersdifferent from the embodiments may also be used. Configurations ofwaveforms unable to be identified by common parameters such as shown inFIG. 8 at (a) and (b) may also be used.

[0029] The level of recording energy means an average energy levelduring a period longer than a thermal relaxation time of a recordingfilm of a recording medium. If the frequency components sufficientlyhigher than that corresponding to a period of a channel bit length (achange unit of edge positions of mark and space) are superposed upon arecording waveform from any reasons, the recording energy level means anaverage energy level during a period longer than that which can neglectthe influence of the frequency components.

[0030]FIG. 1 is a diagram showing an example of the structure of aninformation recording apparatus of this invention. User data 115 to berecorded is temporarily stored in a buffer 114 by a predetermined amountunder the control of a controller 118. Recording data 127 supplied fromthe buffer 114 is converted into a channel data sequence 126 by anencoder 113, the channel data sequence corresponding to the positions ofmarks (not shown) to be formed on a magneto-optical medium 117. Thechannel data sequence 126 is supplied to a recording waveform generator112 whereat it is converted into level control signals 125 correspondingto the recording waveform. The encoder 113 and recording waveformgenerator 112 operate synchronously with a reference timing signal 128generated by a reference timing generator 119. A laser driver 111generates a laser drive current 124 in accordance with the level controlsignals 125 to make a laser 110, as a recording energy source, emitlight in accordance with the recording waveform. A laser light 123radiated from the laser 110 passes through a half mirror 108 and anobjective lens 116 and is converged onto the magneto-optical recordingmedium 117 to heat its recording film (not shown) and form a mark. Inreproducing data, a mark sequence on the magneto-optical recordingmedium 117 is scanned with a laser beam 123 having a low level to theextent that is does not destruct a mark. Light reflected from themagneto-optical recording medium 117 passes through the objective lens116 and half mirror 108 and is incident upon a polarization beamsplitter 107 which splits the reflected light, whose polarizing surfacerotates in a reverse direction in accordance with the mark magnetizationdirection, into orthogonal polarization light beams each being directedvia a detection lens 106 to a photo detector 101. The photo detectors101 convert the orthogonal polarization light beams into electricalsignals proportional to the intensities of the light beams. Eachelectrical signal is amplified by a preamplifier 102 of each photodetector 101 to a sufficient amplitude, and thereafter supplied to adifferential amplifier 102. The differential amplifier 102 amplifies adifference between input signals and generates a magneto-optical signal120 corresponding to a presence/absence of a mark at the scannedposition of the magneto-optical recording medium 117. Themagneto-optical signal 120 undergoes a wave equalizing process at anequalizer and is converted into a binary signal by a comparator 104. Adecoder 105 performs an inverse modulation of the encoder 113 to convertthe binary signal 121 into reproduced data which is stored in the buffer114 by a predetermined amount under the control of the controller 118and output from the apparatus as user data 115.

[0031]FIG. 2 at (a) to (d) is a diagram showing marks and spaces of achannel data sequence and corresponding recording waveforms of thisinvention. FIG. 2 at (a) shows a channel data sequence generated fromrecording data by the encoder. FIG. 2 at (b) shows an image of a marksequence on a recording medium. A recording/reproducing laser light spotis scanned from the left to right in FIG. 2 at (b). Each mark 202 isone-to-one correspondence with each mark of the channel data sequence200, and has a length corresponding to the duration of each mark of thechannel data sequence 200. FIG. 2 at (c) shows an example of a recordingwaveform of the invention corresponding to the channel data sequence 200shown in FIG. 2 at (a). This recording waveform has two differentconfigurations for the record of two marks having the same length of 2L. FIG. 2 at (d) shows another example of a recording waveform of theinvention corresponding to the channel data sequence 200 shown in FIG. 2at (a). This recording waveform has two different configurations for therecord of spaces having the same length of 3 L. A length L is a minimumunit of a change amount of a mark/space length of the channel datasequence 200.

[0032]FIG. 3 is a detailed diagram showing an example of the structureof a recording block 129 shown in FIG. 1. The encoder 113 converts therecording data 127 into the channel data sequence 126 in accordance witha predetermined modulation rule. The channel data sequence 126 is inputto a recording pattern analyzer 302, a mark length latch 300 and a spacelength latch 301. The mark length latch 300 holds a length of each markin the channel data sequence 126 for a predetermined period in a FIFOmanner, whereas the space length latch 301 holds a length of each spacein the channel data sequence 126 for a predetermined period in a FIFOmanner. The mark length and space length held by the latches are inputto a recording pattern analyzer 302. With reference to the channel datasequence 126 supplied from the encoder 113 and the data in the marklength latch 300 and space length latch 301 which data is information ofa preceding recording pattern, the recording pattern analyzer 302generates a Pb control signal 311, a Pa control signal 312, a Pw1control signal 313 and a Pw2 control signal 314 corresponding to anactual recording waveform, in a manner adaptative to the precedingrecording pattern. With reference to these level control signals 125,the laser driver 111 synthesizes the laser drive current 124 and drivesthe laser 110 as the recording energy source. The encoder 113, recordingpattern analyzer 302, mark length latch 300 and space length latch 301operate synchronously with the reference timing signal 128 to transferand generate various signals.

[0033] The channel data sequence output from the encoder is nowclassified into each pair of mark and space, to represent the length ofan n-th (n is a natural number) mark by M(n) and the length of an n-thspace by S(n). The mark length latch 300 holds the immediately precedingmark length M(n) until the immediately succeeding (n+1)-th mark iscompletely recorded, whereas the space length latch 301 holds theimmediately preceding space length S(n) until the immediately succeeding(n+1)-th space is completely recorded. For example, while theinformation recording apparatus records the (n+1)-th mark after the n-thspace, the mark length latch 300 holds the n-th mark length M(n) andsupplies it to the recording pattern analyzer 302 until the informationrecording apparatus completely records the (n+1)-th mark. With referenceto the channel data sequence 126 and the value M(n), the recordingpattern analyzer 302 controls the level control signal 125. For example,in the case of the recording waveform shown in FIG. 2 at (c), if M(n) is3 L or longer, the recording pattern analyzer 302 controls the levelcontrol signal 125 so that the energy level of the start pulse for therecord of the (n+1)-th mark (during the mark forming period) becomesPw3, whereas if M(n) is shorter than 3 L, the recording pattern analyzer302 controls the level control signal 125 so that the energy level ofthe start pulse for the record of the (n+1)-th mark becomes Pw4. In thiscase, the values of Pw3 and Pw4 are assumed to be different. In anotherexample, while the information recording apparatus records the n-thspace after the n-th mark, the mark length latch 300 holds the n-th marklength M(n) and supplies it to the recording pattern analyzer 302 untilthe information recording apparatus completely records the n-th space.With reference to the channel data sequence 126 and the value M(n), therecording pattern analyzer 302 controls the level control signal 125.For example, in the case of the recording waveform shown in FIG. 2 at(d), if M(n) is 3 L or longer, the recording pattern analyzer 302controls the level control signal 125 so that the energy level of a lowlevel period provided at the start for the record of the n-th space(during the mark non-forming period) becomes Tb1, whereas if M(n) isshorter than 3 L, the recording pattern analyzer 302 controls the levelcontrol signal 125 so that the energy level of a low level periodprovided at the start for the record of the n-th space becomes Tb2. Inthis case, the values of Tb1 and Tb2 are assumed to be different. In theabove operation examples, the recording pattern analyzer 302 refers onlyto the immediately preceding mark length or space length as theinformation of the preceding recording pattern. However, thisarrangement does not limit the structure and operation of the marklength latch and space length latch, but two or more mark lengths andspace lengths may be used.

[0034]FIG. 9 is the detailed diagram showing an example of the structureof the recording pattern analyzer 302 shown in FIG. 3. In this example,it is assumed that recording data is (1,7) RLL modulated and thereaftermark edge recorded and that the recording waveform shown in FIG. 2 at(d) is generated. First, the recording data 127 is (1,7) RLL modulatedand thereafter NRZI modulated to be converted into a channel datasequence 126. Next, the channel data sequence 126 is input to a marklength latch 300 and a counter 1000. The mark length latch 300 holds thelength of each mark in the channel data sequence 126 until the start ofthe next mark forming period, and supplies it to a comparator 1002. Thecomparator 1002 compares the mark length with 2 L which is the shortestmark length used by the encoder 113, and judges whether the mark lengthis 2 L or whether it is 3 L or longer. This judgement result istransferred to a waveform encoder 1001. With reference to a referencetiming signal 128 which is a clock signal having a period L, the counter1000 measures a lapse time from the start edge of a mark or space in thechannel data sequence 126 in the unit of L, and supplies the time countresult to the waveform encoder 1001. With reference to the channel datasequence 126, the time count result from the counter 1000 and an outputfrom the comparator 1002, the waveform encoder 1001 exclusivelygenerates a Pb control signal 311, a Pa control signal 312, a Pw1control signal 313 and a Pw2 control signal 314 corresponding to therecording waveform shown in FIG. 2 at (d). These level control signals125 are generated adaptatively to the preceding recording pattern.Specifically in this example, the period while the Pb control signal 311is generated at the start of the mark non-forming period is Tb2 if thelength of the immediately preceding mark in the channel data sequence126 is determined from the comparison result by the comparator to beshortest 2 L, whereas it is Tb1 if the length is determined to be 3 L orlonger. Tb1 and Tb2 are not dependent on the length of each space in thechannel data sequence 126, but have a relationship Tb1>Tb2. In thisexample, therefore, a space length latch is not specifically required.During the other period, in accordance with the lapse time from theleading edge of a mark or space in the channel data sequence 126, thelevel control signals 125 having a predetermined pattern aresequentially output from the waveform encoder 1001. With reference tothese level control signals 125, the laser driver 111 synthesizes alaser drive current 124 and drives the laser 110 as the recording energysource. The whole circuit operates synchronously with the referencetiming signal 128 to transfer and generate various signals.

[0035]FIG. 10 is a diagram illustrating the effects of the recordingpattern analyzer of this invention shown in FIG. 9. This graph shows anexample of measurement results of mark edge positions of a signalreproduced from a mark edge recorded magneto-optical recording medium. Asolid symbolled curve corresponds to a conventional apparatus, and anopen symbolled curve corresponds to the apparatus of this invention. Achange in the shape of a succeeding mark relative to a preceding marklength was measured by fixing the interval between two marks. The markinterval and the succeeding mark length were set to 2 L which was theshortest length of the modulation rule used by the encoder 113, and thepreceding mark length was changed in the range from 2 L to 8 L. A lightspot diameter was about 1.2 μm and a detection window width L was 0.27μm. AE is a shift of a succeeding mark leading edge from an idealposition, the sign of a shift amount being set positive in the delaydirection. The shift amount was plotted as a percentage of ΔE in thedetection window width L. In the case of a conventional apparatus, asthe preceding mark becomes long, the leading edge gradually shifts. Theleading edge shifts greatly if the preceding mark is 3 L or longer, ascompared to the preceding mark of 2 L. In other words, if the precedingmark is 3 L or longer, the succeeding mark is formed considerably largeas compared to the preceding mark of 2 L. If ideal marks can be formed,the edge shifts become constant independent from the preceding marklengths. If the edge shifts are constant, this shift can be removedthrough signal processing. However, if the edge shifts change with thepreceding mark lengths, it is difficult to remove them. Therefore, inorder to achieve stable data recording/reproducing, it is preferable tomake the edge shifts generally constant independently from the precedingmark lengths. In a conventional apparatus, a constant heat compensationperiod (Pb level period shown in FIG. 2 at (d)) for stopping heatingimmediately after the mark forming period is always provided tocompensate for thermal interference corresponding to the preceding spacelength, i.e., position related thermal interference. Namely, thisconstant heat compensation period has been expected to make the edgeshifts generally constant independently from either a preceding marklength or a preceding space length. The reason for this is as follows.The heat conduction effect from the preceding mark and the effect of thepreheat period (Pa level period shown in FIG. 2 at (d)) during the marknon-forming period are balanced and the total effects become generallyconstant so that the immediately succeeding mark can be formed stably.With a conventional apparatus, however, compensation for an input heatamount of a preceding mark, i.e., compensation for a magnitude of heatsource, was not performed. The above-described problem occurs thereforeif a linear recording density is raised and a change in heat conductionfrom the preceding mark to the succeeding mark cannot be neglected.

[0036] As above, a conventional apparatus has a limit in high lineardensity recording. It can be understood from detailed studies of thesolid symbolled curve shown in FIG. 10 that there is a large differenceof the edge shift between the shortest preceding mark length 2 L and themark length 3 L or longer. This means that heat conduction to thesucceeding mark becomes different depending upon whether the precedingmark has a portion longer than 2 L from the trailing edge thereof towardthe upstream direction (opposite to the light spot scanning direction),i.e., whether the preceding mark length is shortest 2 L. Namely, thespace of the succeeding mark becomes different depending upon whetherthere is heat conduction from the portion longer than 2 L from thetrailing edge of the preceding mark toward the upstream direction to thesucceeding mark. In order to form a succeeding mark reliably, theconditions of forming a succeeding mark is required to be changedadaptatively to whether or not the preceding mark has the shortest marklength. The recording waveform shown in FIG. 2 at (d) is generated bythe recording pattern analyzer shown in FIG. 9 by changing theconditions of forming a succeeding mark adaptatively to the precedingmark length. Several methods are conceivable as the method of changingthe conditions of forming a succeeding mark. The recording waveformshown in FIG. 2 at (d) is generated by the recording pattern analyzershown in FIG. 9 by changing the heat compensation period. Specifically,if the preceding mark length is 3 L or longer and excessive heatconduction to the succeeding mark is probable, the heat shielding periodis prolonged to reduce a preheat amount. Therefore, as seen from thewhite plotted curve of FIG. 10, the edge positions of succeeding marksare stable independently from the preceding mark lengths, and nearlyideal marks can be formed. In this example, although the duration of theheat shielding period is changed as a method of changing the conditionsof forming a succeeding mark, other methods may be used such as changingthe recording waveform of a succeeding mark itself as shown in FIG. 2 at(c).

[0037]FIG. 4 at (a) to (j) and FIGS. 5 and 6 show mark sequences andtheir waveforms illustrating the operation of the recording patternanalyzer 302 shown in FIG. 2. FIG. 4 at (a), FIG. 5 at (a) and FIG. 6 at(a) show images of mark sequences to be formed on a recording medium andcorresponding to channel data sequences. L is the minimum unit (channelbit length) of a change amount of a length of each of marks 401, 501 and601 and spaces 402, 502 and 602. A recording/reproducing laser lightspot scans from the left to right in FIGS. 4 to 6 at (a). A target edgeinterval of the marks 401, 501 and 601 and spaces 402, 502 and 602 isalways an integer multiple of

[0038]FIG. 4 at (b) shows a reference timing signal which is a clocksignal of a period T for controlling the recording block. Signalsincluding the recording waveform of the recording block are generatedand transferred synchronously with this clock signal. T corresponds to atime duration of the detection window corresponding to the channel bitlength L, and has a relationship of L=vT where v is a motion speed of alaser light spot. The clock signal is a rectangular wave with a dutyratio of 50%, the high and low level periods each being equal to Tw. Inthis embodiment, there is a relationship of T=2Tw, and the energy levelholding period to be described below is an integer multiple of Tw, i.e.,an integer multiple or a half-odd integer multiple of the period T ofthe reference timing signal.

[0039]FIG. 4 at (c) is a diagram showing an example of a recordingwaveform used by a conventional information recording apparatus. Therecording waveform is mainly classified into a mark forming period and amark non-forming period. In the mark forming period, high level energynecessary for the formation of a mark is intermittently irradiated, andthe mark non-forming period is the period other than the mark formingperiod and corresponds to a space. In the mark forming period, any oneor ones of energy levels Pa, Pb, Pw1 and Pw2 are generated, and in themark non-forming period, energy levels Pb and Pa are consecutivelygenerated. In this recording waveform, fixed energy levels aresequentially generated in a fixed order irrespective of an immediatelypreceding mark or space length, i.e., irrespective of a precedingrecording pattern, only by reflecting a corresponding mark length orspace length. More specifically, the mark forming period correspondingto the mark of 2 L is constituted of a single pulse having a width Twand a level Pw1. As the mark length is elongated at an increment of L, apulse having a width Tw and a level Pw2 is added at a repetition periodof T. The level between the levels Pw1 and Pw2 is always Pb. In the marknon-forming period, a low level period with a width Tb (=3Tw) and thelevel Pb is provided as the start period, and the Pa level is maintainedto the succeeding mark forming period.

[0040]FIG. 4 at (d) is a diagram showing an example of a recordingwaveform used by an information recording apparatus of this invention.In the mark forming period, energy levels are sequentially output in theorder of first Pw1, Pa1, Pw3, Pa2, Pw2 and Pb, and then repetitions ofPw2 and Pb. The upper and lower envelopes of the recording waveformlower as the time lapses after the start of the mark forming period. Theholding time of each level is equal to Tw. In the mark non-formingperiod, a level Pb period is provided by Tb (=3Tw) as the start levelperiod and thereafter the level Pa is maintained to the succeeding markforming period.

[0041]FIG. 4 at (e) is a diagram showing another example of a recordingwaveform used by the information recording apparatus of this invention.In the mark forming period, the upper and lower envelopes of therecording waveform lower as the time lapses after the start of the markforming period. The holding time of each level is equal to Tw. In themark non-forming period, the recording waveform is adaptatively changedwith a preceding recording pattern, i.e., immediately preceding marklength. More specifically, the mark forming period corresponding to themark of 2 L is constituted of a single pulse having a width Tw and alevel Pw1. As the mark length is elongated at an increment of L, a pulsehaving a width Tw and a level Pw2 is added at a repetition period of T.The level between the levels Pw1 and Pw2 is Pa, and the level betweenlevel Pw2 pulses is Pb. In the mark non-forming period, a level Pbperiod is provided as the start period, and the Pa level is maintainedto the succeeding mark forming period. The level Pb period adaptativelychanges to Tb1 (=3Tw) if the preceding mark length is 2 L, and to Tb2(=4Tw) if the preceding mark length is 3 L or longer. In this example,for the simplicity purpose, the energy levels forming the upper envelopeduring the mark forming period are two levels and the energy levelsforming the lower envelope are two levels. The number of energy levelsis not intended to be limitative. For example, as shown in FIG. 4 at(d), three levels or more may be used for forming the upper and lowerenvelopes. This may also be applied to other examples shown in FIG. 4 at(f) to (j) to follow.

[0042]FIG. 4 at (f) is a diagram showing another example of a recordingwaveform used by the information recording apparatus of this invention.In the mark forming period, the upper and lower envelopes of therecording waveform lower as the time lapses after the start of the markforming period. The holding time of each level is equal to Tw. In themark non-forming period, this recording waveform is adaptatively changedwith a preceding recording pattern, i.e., immediately preceding marklength. More specifically, the mark forming period corresponding to themark of 2 L is constituted of a single pulse having a width Tw and alevel Pw1. As the mark length is elongated at an increment of L, a pulsehaving a width Tw and a level Pw2 is added at a repetition period of T.The level between the levels Pw1 and Pw2 is Pa, and the level betweenlevel Pw2 pulses is Pb. In the mark non-forming period, a level Pbperiod is provided by Tb (=3Tw) as the start period, and the Pa1 Pa2level is maintained to the succeeding mark forming period. The levelsPa1 and Pa2 are adaptatively set to Pa1 if the preceding mark length is2 L, and to Pa2 if it is 3 L or longer.

[0043]FIG. 4 at (g) is a diagram showing another example of a recordingwaveform used by the information recording apparatus of this invention.In the mark forming period, the upper and lower envelopes of therecording waveform lower as the time lapses after the start of the markforming period. The holding time of each level is equal to Tw. In themark non-forming period, this recording waveform is adaptatively changedwith a preceding recording pattern, i.e., immediately preceding marklength. More specifically, the mark forming period corresponding to themark of 2 L is constituted of a single pulse having a width Tw and alevel Pw1. As the mark length is elongated at an increment of L, a pulsehaving a width Tw and a level Pw2 is added at a repetition period of T.The level between the levels Pw1 and Pw2 is Pa, and the level betweenlevel Pw2 pulses is Pb. In the mark non-forming period, a level Paperiod is provided by Th1 (=Tw) or Th2 (=2Tw) as the start period, alevel Pb period is thereafter provided by Tb (=3Tw), and the level Pa ismaintained to the succeeding mark forming period. The periods Th1 andTh2 are adaptatively set to Th1 if the preceding mark length is 2 L, andto Th2 if it is 3 L or longer.

[0044]FIG. 4 at (h) is a diagram showing another example of a recordingwaveform used by the information recording apparatus of this invention.In the mark forming period, the upper and lower envelopes of therecording waveform lower as the time lapses after the start of the markforming period. In the mark forming period, the start recording waveformis adaptatively changed with a preceding recording pattern, i.e.,immediately preceding mark length. More specifically, the mark formingperiod corresponding to the mark of 2 L is constituted of a single pulsehaving a width Tw1 (=2Tw) or Tw2 (=Tw) and a level Pw1. As the marklength is elongated at an increment of L, a pulse having a width Tw anda level Pw2 is added at a repetition period of T. The period of thelevel Pw1 adaptatively changes to Tw1 if the preceding mark length is 2L, and to Tw2 if it is 3 L or longer. The level between the levels Pw1and Pw2 is Pa, and the level between level Pw2 pulses is Pb. In the marknon-forming period, a level Pb period is provided by Tb (=3Tw), and thelevel Pa is maintained to the succeeding mark forming period.

[0045]FIG. 4 at (i) is a diagram showing another example of a recordingwaveform used by the information recording apparatus of this invention.In the mark forming period, the upper and lower envelopes of therecording waveform lower as the time lapses after the start of the markforming period. The holding time of each level is equal to Tw. In themark forming period, the start recording waveform is adaptativelychanged with a preceding recording pattern, i.e., immediately precedingmark length. More specifically, the mark forming period corresponding tothe mark of 2 L is constituted of a single pulse having a width Tw and alevel Pw1 or Pw3. As the mark length is elongated at an increment of L,a pulse having a width Tw and a level Pw2 is added at a repetitionperiod of T. The levels Pw1 and Pw3 are adaptatively set to Pw1 if thepreceding mark length is 2 L, and to Pw3 if it is 3 L or longer. Thelevel between the levels Pw1 and Pw2 is Pa, and the level between levelPw2 pulses is Pb. In the mark non-forming period, a level Pb period isprovided by Tb (=3Tw), and the level Pa is maintained to the succeedingmark forming period.

[0046]FIG. 4 at (j) is a diagram showing another example of a recordingwaveform used by the information recording apparatus of this invention.In the mark forming period, the upper and lower envelopes of therecording waveform lower as the time lapses after the start of the markforming period. In the mark forming period, the start recording waveformis adaptatively changed with a preceding recording pattern, i.e.,immediately preceding mark length. More specifically, the mark formingperiod corresponding to the mark of 2 L is constituted of a single pulsehaving a width Tw and a level Pw1 or Pw3. After a period of Tm1 (=2Tw)or Tm2 (=Tw) being provided immediately after this single pulse, as themark length is elongated at an increment of L, a pulse having a width Twand a level Pw2 is added at a repetition period of T. The periods Tm1and Tm2 are adaptatively set to Tm1 if the preceding mark length is 2 L,and to Tm2 if it is 3 L or longer. The level between the levels Pw1 andPw2 is Pa, and the level between level Pw2 pulses is Pb. In the marknon-forming period, a level Pb period is provided by Tb (=3Tw), and thelevel Pa is maintained to the succeeding mark forming period.

[0047]FIG. 5 at (c) is a diagram showing another example of a recordingwaveform used by the information recording apparatus of this invention.In the mark forming period, the lower envelope of the recording waveformlowers as the time lapses after the start of the mark forming period. Inthe mark non-forming period, the recording waveform is adaptativelychanged with its own space length. More specifically, the marknon-forming period corresponding to the space of 2 L is constituted of alevel Pa period with a width of 4 Tw and level Pb periods with a widthTw provided before and after the level Pa period. After the marknon-forming period corresponding to the space of 3 L or longer beingconstituted of a start level Pb period with a width Tb1 (=2Tw) and alevel Pa period with a width Th (=Tw) followed by a level Pb period withthe width Tb2 (=Tw), as the space length is elongated at an increment ofL, the level Pa period with the level Pb periods provided before andafter the level Pa period is elongated by L. The mark forming periodcorresponding to the mark of 2 L is constituted of a single pulse havinga width Tw and a level Pw1. The mark forming period corresponding to themark of 3 L is constituted of a level Pw1 period with the width Twfollowed by a level Pa period with the width Tw and a level Pw1 periodwith the width Tw. Thereafter, as the mark length is elongated at anincrement of L, a level Pw2 pulse with the width Tw is added with alevel Pb period with the width Tw being provided before the level Pw2pulse.

[0048]FIG. 6 at (c) is a diagram showing another example of a recordingwaveform used by the information recording apparatus of this invention.In the mark forming period, the lower envelope of the recording waveformlowers as the time lapses after the start of the mark forming period. Inthe mark non-forming period, the recording waveform is adaptativelychanged with its own space length. More specifically, the marknon-forming period corresponding to the space of 4 L or shorter isconstituted of a start level Pb period with a width Tb1 (=2Tw) and alevel Pa period with a width Th (=Tw) followed a level Pb period withthe width Tb2 (=Tw). After the mark non-forming period corresponding tothe space of 5 L or longer being constituted of the start level Pbperiod with a width Tb2 (=Tw) and a level Pa period with a width Th(=Tw) followed the level Pb period with the width Tb2 (=Tw), as thespace length is elongated at an increment of L, the level Pa period withthe level Pb periods provided before and after the level Pa period iselongated by L. The mark forming period corresponding to the mark of 2 Lis constituted of a single pulse having a width Tw and a level Pw1. Themark forming period corresponding to the mark of 3 L is constituted of alevel Pw1 period with the width Tw followed by a level Pa period withthe width Tw and a level Pw1 period with the width Tw. Thereafter, asthe mark length is elongated at an increment of L, a level Pw2 pulsewith the width Tw is added with a level Pb period with the width Twbeing provided before the level Pw2 pulse.

[0049]FIG. 7 is a graph showing a relationship between a relativerecording power and a jitter, the relationship being obtained throughmark edge recording using recording waveforms of the invention apparatusand a conventional apparatus. The measurement conditions were asfollows. The modulation rule of the encoder used (1,7) codes, an opticalsystem had a light source wavelength of 685 nm, an objective lens has anumerical aperture of 0.55, and the linear recording density was 0.40μm/bit. An open symbolled broken line indicates a jitter (ratio todetection window width) obtained by measuring the interval of leadingedges by using conventional recording waveforms, whereas a solidsymbolled broken line indicates a jitter (ratio to detection windowwidth) obtained by measuring the interval of trailing edges by usingconventional recording waveforms. With conventional recording waveforms,the position of the leading edge of a mark shifts from the idealposition by the influence of the preceding recording pattern. Therefore,the leading edge jitter becomes as a whole larger than the trailing edgejitter. A power which optimizes the leading edge is different from apower which optimizes the trailing edge. In contrast, an open symbolledsolid line indicates a jitter (ratio to detection window width) obtainedby measuring the interval of leading edges by using recording waveformsof the invention, whereas a solid symbolled solid line indicates ajitter (ratio to detection window width) obtained by measuring theinterval of trailing edges by using recording waveforms of theinvention. With recording waveforms of the invention, the leading edgeof the mark is formed generally at an ideal position so that the jittercan be improved as a whole. A power which optimizes the leading edge isthe same as a power which optimizes the trailing edge. Furthermore, thelevels of jitters of the leading and trailing edges are generally equaland the recording power margin is considerably improved.

[0050] According to the present invention, marks can be formed at a highprecision by an information recording apparatus of the type whichrecords data by applying energy to a recording medium to form thereonlocal physical changes of the medium. It is therefore possible to adopta mark edge recording method which is suitable for high linear recordingdensity. Furthermore, by realizing a constant heat accumulation, areproduction crosstalk can be made constant and the track interval canbe shortened. Accordingly, the recording area density can be improved.Since the recording/reproducing operation can be stabilized greatly andat the same time the information recording apparatus and recording mediacan be made compact, the manufacture cost can be reduced.

What is claimed is:
 1. An information recording apparatus for recordingdata by applying energy to a recording medium to form thereon localphysical changes of the medium, the information recording apparatuscomprising: space length discriminating means for discriminating a spacelength of a space in a channel data sequence when data is recorded; andrecording energy irradiating means for generating at least two recordingwaveforms when successive spaces having a same length in the channeldata sequence are recorded, in accordance with results discriminated bythe space length discriminating means.
 2. An information recordingapparatus according to claim 1, wherein the at least two recordingwaveforms are at least two mutually different recording waveforms.
 3. Aninformation recording apparatus for recording data by applying energy toa recording medium to form thereon local physical changes of the medium,the information recording apparatus comprising: space lengthdiscriminating means for discriminating a space length of a space in achannel data sequence when data is recorded; and recording energyirradiating means for switching between at least two levels of a totalenergy irradiating amount during a mark non-forming period when spaceshaving a same length in the channel data sequence are recorded, inaccordance with results of preceding space lengths discriminated by thespace length discriminating means.
 4. An information recording apparatusaccording to claim 3, wherein the spaces having a same length aresuccessive spaces.
 5. An information recording apparatus according toclaim 3, wherein the at least two levels are at least two mutuallydifferent levels.